Search results for " Barrier"
showing 10 items of 540 documents
Uptake of polymeric nanoparticles in a human induced pluripotent stem cell-based blood-brain barrier model: Impact of size, material, and protein cor…
2021
The blood–brain barrier (BBB) maintains the homeostasis of the central nervous system, which is one of the reasons for the treatments of brain disorders being challenging in nature. Nanoparticles (NPs) have been seen as potential drug delivery systems to the brain overcoming the tight barrier of endothelial cells. Using a BBB model system based on human induced pluripotent stem cells (iPSCs), the impact of polymeric nanoparticles has been studied in relation to nanoparticle size, material, and protein corona. PLGA [poly(lactic-co-glycolic acid)] and PLLA [poly(d,l-lactide)] nanoparticles stabilized with Tween® 80 were synthesized (50 and 100 nm). iPSCs were differentiated into human brain m…
Polysorbate-80 coating enhances uptake of polybutylcyanoacrylate (PBCA)-nanoparticles by human and bovine primary brain capillary endothelial cells
2000
Certain drugs such as dalargin, loperamide or tubocurarine are not transported across the blood-brain barrier (BBB) and therefore exhibit no effects on the central nervous system. However, effects on the central nervous system can be observed when these drugs are loaded onto polybutylcyanoacrylate (PBCA)-nanoparticles and coated with polysorbate 80. The mechanism by which these complexed nanoparticles cross the BBB and exhibit their effects has not been elucidated. Cultured microvessel brain endothelial cells of human and bovine origin were used as an in vitro model for the BBB to gain further insight into the mechanism of uptake of nanoparticles. With cells from these species we were able …
Imaging P-Glycoprotein Induction at the Blood–Brain Barrier of a β-Amyloidosis Mouse Model with 11C-Metoclopramide PET
2019
P-glycoprotein (ABC subfamily B member 1, ABCB1) plays an important role at the blood–brain barrier (BBB) in promoting clearance of neurotoxic β-amyloid (Aβ) peptides from the brain into the blood. ABCB1 expression and activity were found to be decreased in the brains of Alzheimer disease patients. Treatment with drugs that induce cerebral ABCB1 activity may be a promising approach to delay the build-up of Aβ deposits in the brain by enhancing clearance of Aβ peptides from the brain. The aim of this study was to investigate whether PET with the weak ABCB1 substrate radiotracer 11C-metoclopramide can measure ABCB1 induction at the BBB in a β-amyloidosis mouse model (APP/PS1-21 mice) and in w…
The extensive and intensive margins of Spanish trade
2011
Recent empirical research highlights that differences in trade flows across countries, products and years are governed by two margins: the intensive margin and the extensive margin. The analysis of the relative contribution of each margin is very important to determine which policies can be more efficient to foster trade at the aggregate, geographic, product or firm level. We use the whole universe of firm level transaction data to analyse the relative contribution of these margins to changes in Spanish trade flows during the 1997–2007 period. We first apply the methodology proposed by Bernard et al. (2009) to decompose trade variation over time into three components: net entry of firms, pr…
Involvement of Microglia in Neurodegenerative Diseases: Beneficial Effects of Docosahexahenoic Acid (DHA) Supplied by Food or Combined with Nanoparti…
2021
Neurodegenerative diseases represent a major public health issue and require better therapeutic management. The treatments developed mainly target neuronal activity. However, an inflammatory component must be considered, and microglia may constitute an important therapeutic target. Given the difficulty in developing molecules that can cross the blood–brain barrier, the use of food-derived molecules may be an interesting therapeutic avenue. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid (22:6 omega-3), has an inhibitory action on cell death and oxidative stress induced in the microglia. It also acts on the inflammatory activity of microglia. These data obtained in vitro or…
Role of oxoproline in the regulation of neutral amino acid transport across the blood-brain barrier.
1996
Regulation of neutral amino acid transport was studied using isolated plasma membrane vesicles derived from the bovine blood-brain barrier. Neutral amino acids cross the blood-brain barrier by facilitative transport system L1, which may allow both desirable and undesirable amino acids to enter the brain. The sodium-dependent amino acid systems A and Bo,+ are located exclusively on abluminal membranes, in a position to pump unwanted amino acids out. gamma-Glutamyl transpeptidase, the first enzyme of the gamma-glutamyl cycle, is an integral protein of the luminal membrane of the blood-brain barrier. We demonstrate that oxoproline, an intracellular product of the gamma-glutamyl cycle, stimulat…
ChemInform Abstract: An ab initio CI Study on the Rotational Barrier of the Allyl Anion.
1986
All-electron and pseudopotential non-empirical calculations have been performed on C 2v and C s (syn, anti) allyl anion conformations. Using a double-zeta valence-shell basis set within the Epstein-Nesbet definition of the unperturbed Hamiltonian, a value about 19 kcal/mol is found for the barrier to rotation of the allyl anion. This value is the theoretical value obtained with greater accuracy, and the lowest one for the rotational barrier.
The ins and outs of cholesterol in the vertebrate retina
2010
Thematic Review Series: Lipids and Lipid Metabolism in the Eye; International audience; The vertebrate retina has multiple demands for utilization of cholesterol and must meet those demands either by synthesizing its own supply of cholesterol or by importing cholesterol from extraretinal sources, or both. Unlike the blood-brain barrier, the blood-retina barrier allows uptake of cholesterol from the circulation via a lipoprotein-based/receptor-mediated mechanism. Under normal conditions, cholesterol homeostasis is tightly regulated; also, cholesterol exists in the neural retina overwhelmingly in unesterified form, and sterol intermediates are present in minimal to negligible quantities. Howe…
Quantum walk on the line through potential barriers
2015
Quantum walks are well-known for their ballistic dispersion, traveling $\Theta(t)$ away in $t$ steps, which is quadratically faster than a classical random walk's diffusive spreading. In physical implementations of the walk, however, the particle may need to tunnel through a potential barrier to hop, and a naive calculation suggests this could eliminate the ballistic transport. We show by explicit calculation, however, that such a loss does not occur. Rather, the $\Theta(t)$ dispersion is retained, with only the coefficient changing, which additionally gives a way to detect and quantify the hopping errors in experiments.
Quenching of bandgaps by flow noise.
2009
We report an experimental study of acoustic effects produced by wind impinging on noise barriers based on two‐dimensional sonic crystals with square symmetry. We found that the attenuation strength of sonic‐crystal‐bandgaps decreases for increasing values of low speed. A quenching of the acoustic bandgap appears at a certain speed value that depends of the barrier filling ratio. For increasing values of low speed, the data indicate that the barrier becomes in a sound source because of its interaction with the wind. We conclude that flow noise has paramount importance in designing acoustic barriers based on sonic crystals. [Work supported by Spanish AECI.]